Join Date: Apr 2003
Location: around in, NJ
Feedback Score: 5 reviews
there is a lot of work to take motorcycle itb's to retrofit them to a car application. this of course, does not mean that it cannot be done.
a few things i can think of:
1. the motorcycle intake port spacing is different than the b18c. the itb's would need to be disassembled to reflect the proper spacing and custom linkages would have to be machined to control throttle activation using the cable mechanism.
2. custom seats would need to be made to attach the itb's to the b18c head. this requires machining and/or welding.
3. custom velocity stacks need to be made/adapted from another application. requires more machining. also custom intake filters of some kind.
4. you need a full ecu to retune the engine. it is just about impossible to tune an engine with itb's using the throttle position vs. MAP method since there is no manifold air pressure. tuning using throttle position and rpm would work but there aren't many EMS's that i know of that can do this...(megasquirt can, motec can...). another option is to house the velocity stacks in a properly designed intake manifold (thus you can tune using the MAP), but this would have to be a custom unit as i do not believe there is a plug-and-play unit available.
5. your powerband will shift very high. itb's would best be paired with a high compression build with very aggressive camshafts to make use of the flow. this happens because the effective runner length created when using itb's is VERY short compared to stock. your stock gsr intake manifold has two stages that effectively changes 'runner volume' and makes the engine more streetable in most driving conditions.
6. i believe when using itb's, you can basically throw away the entire emissions system on the car since it is largly controlled by MAP. then again, if you have reached the point of using itb's on a setup, changes are the setup is pretty drastic and emissions are of no concern anyway.
turnkey itb setups cost a lot of money because a lot of research and machining goes into making them work. the theory behind itb's is pretty simple, but making them work, without the proper tools and knowledge, can become very expensive.